Proper identification of contact lenses is important. Since most contact lens wearers have a different prescription for each eye, the optical power of each contact lens often differs. In addition, the use of an identifying indicium or indicia on a contact lens can be used by the wearer not only as a means of distinguishing lenses from each other, but distinguishing one side of a lens from the other. For example, an indicium or indicia can be used as an inversion indicator to determine if the lens is being put in the eye correctly (i.e. with the proper side of the lens against the eye). Indicia, together, can form lot and batch numbers on the lenses for identification purposes.
Quality control personnel must be able to identify and orient the lens quickly for further inspection. Lens inspectors often have only a limited amount of time to inspect each lens. The lenses must therefore be oriented consistently to begin the inspection process. Often an indicium, or indicia on the lens, such as a logo, is used to orient the lens. Since each individual lens inspection must be done quickly, a highly visible indicium or indicia which assists the inspector in orienting the lens is important.
In many instances, the indicium is difficult to locate due to the lack of contrast between the appearance of the indicia and the lens itself. An identification mark which has sufficient contrast to be easily visible when the lens is not on the eye but relatively invisible when on the eye would be of great advantage to lens wearers, dispensing practitioners, inspectors and anyone who handles such lenses.